From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 83AB9C48BD6 for ; Wed, 26 Jun 2019 21:52:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 640E9214DA for ; Wed, 26 Jun 2019 21:52:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726362AbfFZVwP (ORCPT ); Wed, 26 Jun 2019 17:52:15 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:50424 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726289AbfFZVwO (ORCPT ); Wed, 26 Jun 2019 17:52:14 -0400 Received: from p5b06daab.dip0.t-ipconnect.de ([91.6.218.171] helo=nanos) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1hgFpg-0008Cm-OQ; Wed, 26 Jun 2019 23:52:00 +0200 Date: Wed, 26 Jun 2019 23:51:59 +0200 (CEST) From: Thomas Gleixner To: Fenghua Yu cc: Ingo Molnar , Borislav Petkov , H Peter Anvin , Peter Zijlstra , Andrew Morton , Dave Hansen , Paolo Bonzini , Radim Krcmar , Christopherson Sean J , Ashok Raj , Tony Luck , Dan Williams , Xiaoyao Li , Sai Praneeth Prakhya , Ravi V Shankar , linux-kernel , x86 , kvm@vger.kernel.org Subject: Re: [PATCH v9 15/17] x86/split_lock: Add documentation for split lock detection interface In-Reply-To: <1560897679-228028-16-git-send-email-fenghua.yu@intel.com> Message-ID: References: <1560897679-228028-1-git-send-email-fenghua.yu@intel.com> <1560897679-228028-16-git-send-email-fenghua.yu@intel.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, 18 Jun 2019, Fenghua Yu wrote: > It is useful for development and debugging to document the new debugfs > interface /sys/kernel/debug/x86/split_lock_detect. > > A new debugfs documentation is created to describe the split lock detection > interface. In the future, more entries may be added in the documentation to > describe other interfaces under /sys/kernel/debug/x86 directory. > > Signed-off-by: Fenghua Yu > --- > Documentation/ABI/testing/debugfs-x86 | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+) > create mode 100644 Documentation/ABI/testing/debugfs-x86 > > diff --git a/Documentation/ABI/testing/debugfs-x86 b/Documentation/ABI/testing/debugfs-x86 > new file mode 100644 > index 000000000000..17a1e9ed6712 > --- /dev/null > +++ b/Documentation/ABI/testing/debugfs-x86 > @@ -0,0 +1,21 @@ > +What: /sys/kernel/debugfs/x86/split_lock_detect > +Date: May 2019 > +Contact: Linux kernel mailing list > +Description: (RW) Control split lock detection on Intel Tremont and > + future CPUs > + > + Reads return split lock detection status: > + 0: disabled > + 1: enabled > + > + Writes enable or disable split lock detection: > + The first character is one of 'Nn0' or [oO][fF] for off > + disables the feature. > + The first character is one of 'Yy1' or [oO][nN] for on > + enables the feature. > + > + Please note the interface only shows or controls global setting. > + During run time, split lock detection on one CPU may be > + disabled if split lock operation in kernel code happens on > + the CPU. The interface doesn't show or control split lock > + detection on individual CPU. But it should show that the debug output for the kernel has been globally disabled instead of merily stating 'enabled' while it's already disabled on a bunch on CPUs. I fundamentally despise inconsistent information. Even in debugfs files inconsistency is a pain because it make debugging via mail/ bugzille etc. unnecessarily cumbersome. Thanks, tglx